Dispersible flushable moist products need to exhibit satisfactory in-use strength, but quickly break down in sewer or septic systems. Current dispersible moist wipes do this by using a triggerable, salt-sensitive binder on a substrate made from cellulose-based fibers. The binder attaches to cellulose fibers to form a network having adequate in-use strength in a salt solution, but swells and disintegrates in the fresh water of a toilet and sewer system. Electrolytes such as sodium chloride and sodium benzoate are used to keep a moist wipe intact until diluted with water.
There is a great desire to provide higher order skin benefits and aesthetic properties to dispersible moist wipes. One way to do this is by wetting the wipe substrate with a wetting composition such as an emulsion that includes therapeutic amounts of silicone oil as a skin barrier. Emulsions are preferred over solutions because they can impart oils to the skin for the prevention of diaper dermatitis (diaper rash) and provide benefits such as emolliency, moisturization whereas solutions cannot. However, while emulsions present benefits, problems arise when using them as dispersible, moist-wipe wetting compositions. The biggest problem to overcome is the phase separation that occurs when combining electrolytes and oils at therapeutic concentrations in an emulsion.
While there are several methods to achieve stable emulsions having a combination of electrolytes and oils at the specified concentrations, there are several disadvantages associated with these methods. First, the concentration of emulsifier required to successfully stabilize an emulsion containing a silicone oil, such as dimethicone can be so great that it is cost prohibitive. Second, obtaining a low-viscosity, sprayable solution can be difficult due to the high probability that oil droplets will coalesce, particularly at the elevated temperatures to which the solution may be exposed. Third, without appropriately modifying the rheology of the water phase, emulsions with a low viscosity and low solids content tend to undergo phase separation, particularly following a freeze-thaw cycle. This results in a product that would not be efficacious because some areas of the wipe would have higher concentrations of the oil and other areas with less or even no oil present.
There remains a need for a cost-effective, dispersible moist wipe with an emulsion-based wetting composition that does not phase separate with the addition of an electrolyte, even after a freeze-thaw cycle. It would be further advantageous if such wetting composition had a viscosity suitable for spraying onto a wipe substrate.